The Pope also affirmed the importance of the monogamous and indissoluble character of marriage, when he met the prelates today in an audience.
"For the Christian, traditional forms of marriage can never be a substitute for sacramental marriage," the Pope said in his address to the bishops, who were concluding their five-yearly visit to Rome.
In recent days the Holy Father met privately with the bishops and read reports from them. Today he stated his concerns "about the proper celebration of Christian marriage in Ghana."
"I share your concern and therefore invite the faithful to place the sacrament of matrimony at the center of their family life," Benedict XVI said in his English-language address.
"While Christianity always seeks to respect the venerable traditions of cultures and peoples, it also seeks to purify those practices which are contrary to the Gospel," he declared, in an implicit reference to the polygamous traditions found in the western African nation of 22 million.
"For this reason," the Pope continued, "it is essential that the entire Catholic community continue to stress the importance of the monogamous and indissoluble union of man and woman, consecrated in holy matrimony."
The Holy Father explained to the bishops that it is the "Church's task to assist Christian families to live faithfully and generously as true 'domestic churches.'"
"In fact, sound catechesis relies on the support of strong Christian families which are never selfish in character, constantly directed toward the other and founded upon the sacrament of matrimony," Benedict XVI said.
"A solid catechetical foundation," he said, will give Catholics "the necessary tools to confront the challenges of changing economic realities, globalization and disease."
"It will also assist them in responding to the arguments often put forward by religious sects," the Pope added. "Consequently, it is important that future pastoral planning at both national and local levels carefully takes into account the needs of the young and tailors youth programs to address these needs appropriately."